Generate a 36-character (128-bit) Universally Unique IDentifier (v4)

generateUUID.js

/**
 * Generate a 36-character (128 bit) Universally Unique IDentifier (v4)
 * @param {Number} length [Optional] length of the output string (default = 36)
 * @param {String} str [Optional] string to start with
 */
function UUID(length = 36, str = '') {
    let a = 36 - length + str.length
    while (a++ < 36) {
        str +=
            (a * 51) & 52
                ? (a ^ 15
                      ? 8 ^ (Math.random() * (a ^ 20 ? 16 : 4))
                      : 4
                  ).toString(16)
                : '-'
    }
    return str
}